1. Technical Field
Embodiments of the present disclosure relate generally to power supply circuits, and more specifically to a DC-DC converter with improved efficiency at low load currents.
2. Related Art
A DC-DC converter is a circuit that generates a regulated direct current (DC) output voltage from a power source such as, for example, an unregulated DC input voltage. A regulated output voltage generally refers to a constant-value output voltage despite changes in the value of the current drawn (within a range) from the converter. The regulated DC output voltage of a DC-DC converter may be used as a power supply for powering electronic circuits, the electronic circuits thus constituting a load(s) and drawing a load current from the DC-DC converter. DC-DC converters may include linear as well as switching converters. A switching (or switch-mode) DC-DC converter generally refers to a converter that employs transistors operated to be switched ON and OFF to generate the desired output DC voltage from the input DC voltage. A switching DC-DC converter may employ a smoothing circuit (e.g., filters, using inductors and capacitors) to obtain a constant value DC voltage from a pulsed/switching output voltage generated by the switching operation of the transistors. Linear converters refer to DC-DC converters in which the resistance of a transistor operated in the linear region is controlled to generate a desired output DC voltage from an input DC voltage.
Efficiency of a DC-DC converter is generally the ratio of the total output power delivered to a load (or loads) powered by the output of the DC-DC converter and the total power consumed by the DC-DC converter in delivering the output power, and may be specified, for example, as a percentage. The efficiency of a DC-DC converter may be poorer (smaller) at low load currents than at relatively higher load currents. For example, one or more circuit portions or functional blocks of a mobile phone may be powered-down when the mobile phone is not being used to process voice calls and/or when other utilities and applications provided by the mobile phones are not being used. In such a scenario, the load current drawn by the mobile phone from a DC-DC converter used to supply power to the mobile phone may be termed to be ‘low’ compared to, for example, when the mobile phone is being used to make voice calls.